WASHINGTON — If you’re feeling a surge of optimism over the Phillies’ chances of finally returning to the playoffs, it’s probably because they’ve reeled off 11 wins in 13 games since firing the manager. Or maybe it’s because they’re averaging 6.4 runs per game in June. But here’s one more reason to buy Phillies stock: Nearly 20% of their remaining games are against the Washington Nationals. A revised schedule after the owners’ lockout forced the Phillies to wait 64 games to get a look at what has become of their division rival, and well, they feasted. They scored seven — yes, seven — unearned …